Group III-V compound semiconductors such as GaN and AlGaN are widely used for optoelectronics, electronic devices and the like, owing to many advantages such as, for example, a wide and easily adjustable band gap energy.
In particular, light-emitting elements such as light-emitting diodes or laser diodes using group III-V or II-VI compound semiconductors may realize various colors of light such as, for example, red, green, and blue light, as well as ultraviolet light, via the development of device materials and thin-film growth technique, and may also realize white light having high luminous efficacy via the use of a fluorescent material or by combining colors. These light-emitting elements have advantages of low power consumption, a semi-permanent lifespan, fast response speed, good safety, and eco-friendly properties compared to existing light sources such as, for example, fluorescent lamps and incandescent lamps.
Accordingly, the application of light-emitting elements has been expanded to a transmission module of an optical communication apparatus, a light-emitting diode backlight, which may substitute for a cold cathode fluorescent lamp (CCFL) constituting a backlight of a liquid crystal display (LCD) apparatus, a white light-emitting diode lighting apparatus, which may substitute for a fluorescent lamp or an incandescent bulb, a vehicle headlight, and a signal lamp. In recent years, light-emitting elements, which emit light within an ultraviolet wavelength range, have been used in various sterilization devices.
FIG. 1 is a view illustrating a light-emitting element of the related art.
In the light-emitting element 100 of the related art, a light-emitting structure 120, which includes a first conductive semiconductor layer 122, an active layer 124, and a second conductive semiconductor layer 126, may be formed on a substrate 110, a light-transmissive conductor layer 140 may be disposed on the light-emitting structure 120, a second electrode 166 may be disposed on the light-transmissive conductor layer 140, and a first electrode 162 may be disposed on the first conductive semiconductor layer 122.
The light-emitting element 100 emits light having energy determined by the inherent energy band of a constituent material of the active layer 124 in which electrons injected through the first conductive semiconductor layer 122 and holes injected through the second conductive semiconductor layer 126 meet each other. The light emitted from the active layer 124 may be changed depending on the composition of the constituent material of the active layer 124.
The light-transmissive conductor layer 140 is disposed in consideration of poor current injection from the second electrode 166 to the second conductive semiconductor layer 126. The light-transmissive conductor layer 140 is in tight contact with the second conductive semiconductor layer 126, and consequently, exhibits excellent current injection efficiency, but may absorb the light emitted from the active layer 124, which may cause deterioration in the luminous efficacy of the light-emitting element 100.